Inhalers have become wide spread for treating i. e. respiratory disorders, diabetes, osteoporosis and pain. The inhaler devices are clinically validated together with the specific drug for a specific therapy. When new issues come up that need to be clinically substantiated combined with a need of better clinical cost/benefit ratio by obtaining more reliable use pattern data from fewer test persons, or there is a need for new features like compliance feedback to the user, there is a demand for implementing electronic event data logging with inhalers. To avoid redesigning the inhalers and the associated costly clinical trials, there is a need for an add-on device, which does not imply any intervention into the inhaler, thus still logging or providing relevant reliable data regarding dose loading and inhalation flow.
U.S. Pat. No. 5,505,195 describes an electronic device to be attached to a standard dry powder inhaler, but the description reveals that the flow sensors disclosed interfere with the mechanical design of the inhaler and will therefore not conform to the demands above. GB-2262452 discloses several techniques for flow measurements within inhalers, but they all measure the flow inside the inhaler flow path and will therefore not conform to the above requirements. Other inhalers may be seen in US2004/0069301 and GB2398065. There is, therefore, a need of an invention to solve and fulfil the demand for a true non-intervening add on monitoring device for existing inhalers.